Yesware will automatically sync the meeting with the Contact or Lead in Salesforce associated with the first email address added as a guest to the calendar invite. You can also manually select a contact or lead and account or opportunity.
It will sync it to Salesforce as an Event under the Activity history.
If no match is found and you don’t manually enter a record, then it will sync the event to Salesforce with no associated Contact/Lead and Account/Opportunity.
All Events that Yesware logs into Salesforce using Google Calendar Sync will have "[event synced]" added to the Description field of the event.
This is only added to the Salesforce event and is not included in your Google Calendar event.